<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script type="text/javascript">
        function draw() {
            var canvas = document.getElementById('canvas');
            if (canvas.getContext) {
                var ctx = canvas.getContext('2d');

                // 二次贝塞尔曲线
                ctx.beginPath();
                ctx.moveTo(75,25);
                ctx.quadraticCurveTo(25,25,25,62.5);
                ctx.quadraticCurveTo(25,100,50,100);
                ctx.quadraticCurveTo(50,120,30,125);
                ctx.quadraticCurveTo(60,120,65,100);
                ctx.quadraticCurveTo(125,100,125,62.5);
                ctx.quadraticCurveTo(125,25,75,25);
                ctx.stroke();
            }
        }
    </script>
</head>
<body>
<body onload="draw()">
<canvas id="canvas" width="300px" height="300px"></canvas>
</body>
</body>
</html>